Why is my external DAC not working with iOS 18?

hi,

I have an iPhone 13 mini iOS 18.0.1 with a Lightning Apple camera adapter (A1619 firmware 1.0.5) on which I plugged an external Dac (cowon plenue 2) using a otg usb cable. My setup worked with ios17 and does not work anymore with ios18. When my Dac switches in USB Dac mode, the sound continue to be played on the iPhone. I tested it with the Apple Music app and Qobuz app, same problem.

would you have an idea how to output sound from iPhone to external Dac with ios18 ?

thanks

[Re-Titled by Moderator]